Please use this identifier to cite or link to this item: https://hdl.handle.net/11147/10096
Title: Effects of mechanical treatment on the formation of alpha-Al2O3 from gibbsite
Authors: Şakar Deliormanlı, Aylin
Çiftçioğlu, Muhsin
Polat, Hürriyet
Şakar Deliormanlı, Aylin
Çiftçioğlu, Muhsin
Polat, Hürriyet
Izmir Institute of Technology. Chemistry
Keywords: gibbsite
alpha-alumina
phase transformation
grinding
ultrasonic treatment
Issue Date: 2004
Publisher: Trans Tech Publications
Series/Report no.: Key Engineering Materials
Abstract: In this study preparation of fine alpha alumina powders derived from Bayer gibbsite was studied. Preparation of the alumina powders was performed by decomposition of the gibbsite into transition alumina phase followed by controlled transformation to the alpha phase. Gibbsite was thermally treated at 350degreesC and 900degreesC to obtain a transition form of alumina. The purpose of the heat treatment at 350degreesC was to increase the surface area of the gibbsite particles and obtain a loosely packed structure that may reduce the size of the rather coarse precursor gibbsite during the grinding step. Mechanical treatment (by using ultrasonic forces and impact forces) was utilized to increase the transformation rate to the alpha alumina in the transition phase matrix and influence the nucleation and growth rate of the solid-solid phase trans format ion. These powders were calcined at 1100, 1200 and 1450degreesC for 1 to 8 hours. Results indicated that transformation to the alpha phase was accomplished in the powders preheated at 900degreesC, ultrasonically treated or ground, and then calcined at 1200degreesC for 2 to 8 hours or at 1450degreesC for 2 hours. Ultrasonic treatment accelerated the transformation rate to the alpha phase at 1100degreesC in 2 hours. Powders that were calcined at 1100 to 1200degreesC for I hour had a significant kappa content together with the alpha phase. Additionally the powder prepared without mechanical treatment and calcined at 1100degreesC was mainly in the kappa phase.
Description: 8th Conference of the European-Ceramic-Society
URI: https://hdl.handle.net/11147/10096
ISBN: 0-87849-946-6
ISSN: 1013-9826
Appears in Collections:WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

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